Lithium Bis(fluorosulfonyl)imide/Poly(ethylene oxide) Polymer Electrolyte for All Solid-State Li–S Cell

Solid polymer electrolytes (SPEs) comprising lithium bis­(fluorosulfonyl)­imide (Li­[N­(SO₂F)₂], LiFSI) and poly­(ethylene oxide) (PEO) have been studied as electrolyte material and binder for the Li–S polymer cell. The LiFSI-based Li–S all solid polymer cell can deliver high specific discharge capacity of 800 mAh g_sulfur^–1 (i.e., 320 mAh g_cathode^–1), high areal capacity of 0.5 mAh cm^–2, and relatively good rate capability. The cycling performances of Li–S polymer cell with LiFSI are significantly improved compared with those with conventional LiTFSI (Li­[N­(SO₂CF₃)₂]) salt in the polymer membrane due to the improved stability of the Li anode/electrolyte interphases formed in the LiFSI-based SPEs. These results suggest that the LiFSI-based SPEs are attractive electrolyte materials for solid-state Li–S batteries

Polymer-Rich Composite Electrolytes for All-Solid-State Li–S Cells

Polymer-rich composite electrolytes with lithium bis­(fluorosulfonyl)­imide/poly­(ethylene oxide) (LiFSI/PEO) containing either Li-ion conducting glass ceramic (LICGC) or inorganic Al₂O₃ fillers are investigated in all-solid-state Li–S cells. In the presence of the fillers, the ionic conductivity of the composite polymer electrolytes (CPEs) does not increase compared to the plain LiFSI/PEO electrolyte at various tested temperatures. The CPE with Al₂O₃ fillers improves the stability of the Li/electrolyte interface, while the Li–S cell with a LICGC-based CPE delivers high sulfur utilization of 1111 mAh g^–1 and areal capacity of 1.14 mAh cm^–2. In particular, the cell performance gets further enhanced when combining these two CPEs (Li | Al₂O₃–CPE/LICGC–CPE | S), reaching a capacity of 518 mAh g^–1 and 0.53 mAh cm^–2 with Coulombic efficiency higher than 99% at the end of 50 cycles at 70 °C. This study shows that the CPEs can be promising electrolyte candidates to develop safe and high-performance all-solid-state Li–S batteries